Fuel injection system for externally ignited internal combustion engines

ABSTRACT

In a fuel injection system, a flow rate-responsive device disposed in the suction tube of an internal combustion engine angularly displaces a control plunger which has an oblique control edge and which forms part of a fuel metering device. Depending upon the angular position of said plunger, said control edge determines a flow passage section for the fuel to control the air-fuel mixture.

United States Patent Eckert 1451 sepns, 1972 [54] FUEL INJECTION SYSTEM FOR EXTERNALLY IGNITED INTERNAL COMBUSTION ENGINES statt, Germany Assignee: Robert Bosch, GmbH,

Gennany Filed: Jllly 9, 1970 Appl. No.: 53,540

July 9, 1969 Inventor: Konrad Eckert, Stuttgart-bad Canni Stuttgart,

Foreign Application Priority Dam l l Germany P 19 34 703.6

U.s. c1. ..123/119 n, 12s/32 R l im. c1. Fozb 33/00, Fozm 39/00 Field of Search ..123/119 R, 139.17, 140.2, 140.3,123/32 EA,32 Jv, 33,33 J 33 C, 32 AE,

198 DB, 179 G, 139, 140; 251/636; 239/87,y

References cited In a lfuel injection system, a flow rate-responsive device disposed in the suction tube of an internal combustion engine angularly displaces a control plunger which has an oblique control edge and which forms part'of a f'uleterndeE'Dpedig"upon the angular position of said plunger, said control edge determines a flow `passage section for the fuel to control the air-fuel mixture.

4 Claims, 1 Drawing Flgure PATENTED sfr 5 |912 3 6 88 7 54 INV EN TOR.

FUEL INJECTION SYSTEM FOR EXTERNALLY IGNITED INTERNAL COMBUSTION ENGINES BACKGROUND OF THE INVENTION This invention relates to a fuel injection system for extemally ignited internal combustion engines and is of the type wherein the fuel is injected continuously into the 'suction tube in which there are disposed in series an arbitrarily operable butterfly valve and a throttle member. The latter, actuated by the upstream and downstream pressure prevailing in the suction tube, controls a metering valve disposed in the fuel conduit and operating with a constant pressure drop.

In a known fuel injection system of the aforenoted l type (such as disclosed in German Pat. No. 1,243,917), the throttle member displaces the throttle needle of the fuel metering valve, the contour of which is designed in such a manner that for each flow rate of air there corresponds a predetermined flow rate of fuel. For this purpose, the momentary flow passage section of the throttle member may be made proportionate to the momentary flow passage section of the fuel metering valve.

The shaping of the throttle needle contour is relatively expensive. Further, in particular, the adjustment of the throttle needle and throttle bore of the fuel metering valve with respect to the position of the throttle member, as well as the alteration of the fuel-air mixture during operation of a hot engine or for providing a rich mixture of the starting fuel quantities, are restricted to relatively narrow limits.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection system of the aforenoted type wherein the mentioned disadvantages are eliminated.

Briefly stated, according to the invention the fuel metering valve includes a control plunger which is provided with an oblique control edge and which is turnable by the throttle member. The'angular position of the control plunger determines the flow passage section for the fuel.

The invention will be better understood, as well as showing the embodiment in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT In avsuction tube l, intake air flows past a throttle member 2 and an arbitrarily operable butterfly valve 3 55 to a cylinder or cylinders (not shown) of an internal combustion engine (also not shown).

A cylindrical throttle member 2 extends transversely tothe direction of air flow into the suction tube l through an orifice 4 provided in the tube wall. It is to be understood that the said cylindrical throttle member may be replaced by a pivoting gate or a baffle plate displaceable in the direction of air flow. The displacement of the throttle member 2 in the suction tube 1 is approximately a linear function of the air quantity passing through the suction tube l. The pressure prevailing between the throttle member 2 and the butterfly valve 3 remains approximately constant assuming a constant pressure upstream of the throttle member 2.

The throttle member 2 is integral with a piston 5, the diameter of which i greater than that of the throttle member 2. The piston 5 is received with a snug tit by and is displaceable in a cylinder 6. The piston 5 is pulled radially outwardly of the suction tube 1 against the return force of a spring 9 by means of the vacuum prevailing in the suction tube portion la between the throttle member 2 and the butterfly valve 3. The vacuum conditions prevailing in the suction tube portion 1a are communicated to cylinder 6 through a channel 8. The annular space defined in the cylinder 6 by the throttle member 2 and the adjacent radial annular face of the piston 5 communicates by means of a channel 7 either with the atmosphere or, as shown, with the air inlet 1d of the suction tube 1. It is to be understood that instead of piston 5, the throttle member 2 may be associated with a membrane or any other equivalent actuating means. The slope of the linear function between the displacement of the throttle member 2 and the air quantity depends upon the characteristic of the spring 9, as well as upon the frictional losses between the contacting faces of the sliding members. To the throttle member 2 there is affixed, for simultaneous displacement therewith, a toothed rack 10, the teeth of which mesh with a pinion 12 which is arranged circumferentially about a tumable control plunger 11. The latter forms the movable part of the fuel metering valve. It is thus seen that to each axial position of the throttle member 2 there corresponds a determined angular position of the control plunger 1 1.

In the lateral face of the control plunger 11 there is provided an annular groove 14, one axial boundary of which is formed as an oblique control edge 14' for con trolling the flow passage section 22 of a preferably rectangular longitudinal groove l5. A fuel pump 16, which may be driven, for example, by an electric motor (not shown), draws fuel from a tank 17 and delivers it through a conduit 18 into the annular groove 14. From the conduit 18 there extends, immediately downstream of pump 16, a return conduit 19 in which there is arranged a pressure limiting valve 20.

From the annular groove 14 the fuel flows through the metering flow passage section 22 into the groove 15 and therefrom into a bore 23 which leads to a plunger valve 24. The latter, which maintains the pressure drop at the metering throttle 22 at a constant valve, includes an annular chamber 2S into which merges the bore 23 and a control plunger 26 which is actuated by a membrane 27. The lateral face of the control plunger 26 is provided with an annular groove 28 which communicates with a conduit 29 leading to the fuel injection valve or valves 34 (only one shown). One axial boundary of the groove 28 controls the flow passage section defined jointly by the groove 28 and the chamber 25.

The spaces at either side of the membrane 27 are connected hydraulically by means of conduits with locations upstream of and downstream of the metering throttle 22. Thus, the space 27', in which hydraulic pressure tends to displace'the valve 24 in the closing direction upon increasing fuel pressure upstream of throttle 22, is connected by means of a conduit 30 with a conduit 18. The space 27" on the other hand, in which hydraulic pressure tends to displace the valve 24 in the opening direction, is connected by a channel 3l with the conduit 23. If the pressure changes upstream of the metering throttle 22 or downstream thereof (for example, in the conduit 29) and, as a result, the pressure drop at the metering throttle 22 is changed, the control plunger 26 is, by means of the membrane 27, displaced against the force of a return spring 33. Such displacement is in progress until, by virtue of the throttle effect of the slide valve 24, the previous pressure drop at the metering throttle 22 is re-established. The pressure drop is determined mainly by the stiffness of the membrane 27 and the force of the spring 33. The pressure drop is thus constant and independent of the fuel quantities flowing through the fuel conduit 29.

The control plunger 11 is axially displaceable against the force of a return spring 35 which presses it against a fixedly but adjustably held abutment 36. For changing the fuel-air mixture, the abutment 36 is,arbitrarily or by means of a suitable device, rotatable whereby the ratio of the flow passage section of the throttle member 2 to that of the fuel metering throttle 22 is varied. Such setting is effected for the pre-adjustment of the flow passage section ratio and also, during starting or hot run of the engine if a richer air-fuel mixture is required.

The terminus of the control plunger l1 remote from the abutment 36 is surrounded by an electromagnet 37. When the latter is energized, the control plunger 11 is displaced axially against the force of a return spring 35. Upon such an occurrence, hydraulic communication is interrupted between the annular groove 14 and the groove so that the flow of fuel into the fuel injection valve or valves 34 is cut off. This is particularly required during pushing operation to avoid an excessive ratio of poisonous matter in the exhaust and to prevent a jerky operation of the engine.

Each fuel injection valve 34 is provided with a closing member 38 which, during the pushing operation, is, by hydraulic pressure, displaced against the force of a return spring 39 closing thereby the nozzle opening 40. In this manner it is prevented that during the pushing operation, fuel is drawn from the fuel conduit 29. Such occurrence would again result in the aforenoted disadvantages. For a hydraulic control of the closing member 38 there is provided a conduit 41 which coinmunicates with an annular groove 42 disposed on the lateral face of the control plunger 11. The annulai groove 42, in turn, communicates through a channel 43 with a chamber receiving the spring 35. In channel 43 there is disposed a pressure maintaining valve 44. The latter has solely the purpose to prevent the fuel present in the conduits and channels 41, 42 and 43 from escaping. It does not prevent, however, the closure member 38 of the fuel injection valve 34 from being displaced by the spring 39 into its initial position as shown when the control plunger 11 is in a position as illustrated in the drawing.

As soon as the control plunger l1 is displaced by the electromagnet 37 and thereby the fuel admission to the fuel injection valve or valves 34 is interrupted, the annular groove 14 of the control plunger 1 l is connected with the conduit 4l, whereby the fuel delivered by the pump 16 exerts a pressure on the closing member 38 with a force determined by the pressure control valve 20. As a result, the lclosing member 38 is displaced against the force of the return sprin 39 and closes the injection nozzle 40. It is thus seen at simultaneously with the interruption of the fuel admission, the fuel injection nozzle 40 is also closed.

In the conduits 29 and 41 there are disposed distributors 45 and 46, respectively, which have as many branch conduits as there are fuel injection valves 34 as sociated with the fuel injection system.

What is claimed is:

1. In a fuel injection system associated with an externally ignited internal combustion engine, said system being of the type that includes (A) a suction tube through which air is drawn to said engine, (B) an arbitrarily operable butterfly valve disposed in said suction tube, (C) a throttle member disposed in said suction tube in series with said butterfly valve and displaceable as a function of the upstream and downstream air pressure (D) fuel injection means to introduce fuel into the stream of intake air for obtaining a fuel-air mixture, (E) fuel conduit means to deliver fuel to said fuel injection means and (F) a fuel metering valve operating with a constant pressure drop in said fuel conduit means and actuated by said throttle member for controlling the flow of fuel to said fuel injection means, the improvement comprising,

(A) a control plunger forming pait of said fuel metering valve, said plunger including an oblique control edge determining a flow passage section for said fuel in said fuel conduit means, said control plunger being axially displaceable for entirely closing said flow passage section to cut off fuel supply to said fuel injection means and (B) means connecting said throttle member with said control plunger for turning the latter in response to the displacement of said throttle member to vary said flow passage section.

2. An improvement as defined in claim 1, including electromagnetic means for controlling the axial displacement of said control plunger.

3. An improvement as defined in claim l including A. a closing member movable in said fuel injection means for cutting off the injection of fuel when moved in a closed position,

B. a hydraulic control conduit leading from said control plunger to said closing member and C. means provided on said control plunger to establish communication between the pressure side of said fuel conduit means and said hydraulic control conduit for moving said closing member into said closed position when said control plunger is axially displaced for closing said flow passage section.

4. An improvement as defined in claim 3, wherein said means provided on said control plunger to establish said communication is an annular groove, one axial boundary of which is formed by said oblique control edge. 

1. In a fuel injection system associated with an externally ignited internal combustion engine, said system being of the type that includes (A) a suction tube through which air is drawn to said engine, (B) an arbitrarily operable butterfly valve disposed in said suction tube, (C) a throttle member disposed in said suction tube in series with said butterfly valVe and displaceable as a function of the upstream and downstream air pressure (D) fuel injection means to introduce fuel into the stream of intake air for obtaining a fuel-air mixture, (E) fuel conduit means to deliver fuel to said fuel injection means and (F) a fuel metering valve operating with a constant pressure drop in said fuel conduit means and actuated by said throttle member for controlling the flow of fuel to said fuel injection means, the improvement comprising, (A) a control plunger forming part of said fuel metering valve, said plunger including an oblique control edge determining a flow passage section for said fuel in said fuel conduit means, said control plunger being axially displaceable for entirely closing said flow passage section to cut off fuel supply to said fuel injection means and (B) means connecting said throttle member with said control plunger for turning the latter in response to the displacement of said throttle member to vary said flow passage section.
 2. An improvement as defined in claim 1, including electromagnetic means for controlling the axial displacement of said control plunger.
 3. An improvement as defined in claim 1, including A. a closing member movable in said fuel injection means for cutting off the injection of fuel when moved in a closed position, B. a hydraulic control conduit leading from said control plunger to said closing member and C. means provided on said control plunger to establish communication between the pressure side of said fuel conduit means and said hydraulic control conduit for moving said closing member into said closed position when said control plunger is axially displaced for closing said flow passage section.
 4. An improvement as defined in claim 3, wherein said means provided on said control plunger to establish said communication is an annular groove, one axial boundary of which is formed by said oblique control edge. 